<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>控制结构</title>
</head>
<body>
<h1>文章列表</h1>
{% if num <= 0 %}
    <h2>文章数量为0，没有内容可演示</h2>
{% else %}
    {% for article in articles %}
        <h2>{{ article.title }}</h2>
        <p>{{ article.content}}</p>
    {% endfor%}
{% endif %}
</body>
</html>